David Kirkpatrick

August 14, 2008

Nanotubes help create stretchy conductors

This application of carbon nanotubes could feasibly lead to displays or even computers that are stretchable and can wrap around objects. This is an early step toward wearable computers and actual “walking billboards.” And there are many, many uses not even considered just yet.

These are very exciting times with all the innovation going on in many fields, nanotech being one of the more interesting because there is so much promise there and so many unknowns to be discovered. A lot of these developmentss really are science fiction coming to pass.

This Technology Review article covers the University of Tokyo research that led to the stretchable conductors.

From the link:

To make the stretchable polymer conductive, Someya’s group combined a batch of millimeter-long, single-walled carbon nanotubes with an ionic liquid–a liquid containing charged molecules. The resulting black, paste-like substance was then slowly added to a liquid polymer mixture. This produced a gel-like substance that was poured into a cast and air-dried for 24 hours.

The benefit of adding the nanotubes to a polymer before it is cast, says Someya, is that the nanotubes, which make up about 20 percent of the weight of the total mixture, are more evenly distributed. And because each nanotube is about a millimeter in length, there’s a high likelihood that in aggregate they will form an extensive network that allows electrical charge to propagate reliably throughout the polymer.

Previously, researchers have added micrometer-length carbon nanotubes to polymers, says Ray Baughman, a professor of materials science at the University of Texas. Most often, they would simply coat the polymer with nanotubes. Baughman says that Someya’s work is exciting, but he notes that he would have expected that adding higher percentages of carbon nanotubes to polymers reduces their stretchiness.

According to Someya, the initial air-dried nanotube-polymer film is flexible but not that stretchable. In order to improve its stretchiness, a machine perforates it into a net-shaped structure that is then coated with a silicone-based material. This enables the material to stretch much farther without compromising its conductivity.

A researcher stretches a mesh of transistors connected by elastic conductors that were made at the University of Tokyo.

Malleable matrix: A researcher stretches a mesh of transistors connected by elastic conductors that were made at the University of Tokyo.

July 16, 2008

Long-life Flash memory chips

Filed under: Technology — Tags: , , , , — David Kirkpatrick @ 2:00 pm

Great news in storage tech:

Current Flash chips are estimated to have a useful lifetime of around a decade for most applications.

However, some applications that require repeated writing and rewriting of data can theoretically cause cells to wear out much faster, sometimes rendering a Flash device useless within a few years.

This can happen when a large area of Flash memory is used as a swap file or virtual memory, or to store constantly updated log files.

The continuing miniaturisation of conventional Flash memory chips also threatens to reduce their lifetime.

This and other factors make conventional high-density Flash cells unworkable at circuit sizes below 20 nanometres, the scientists claim.

The new ferroelectric Nand Flash memory cell developed by the Japanese scientists can be scaled down to at least 10 nanometres. The next generation of conventional flash cells will use a 30 nanometre circuit density.

The ferroelectric Flash memory cell can be rewritten more than 100 million times, compared to a conventional cells lifetime of around 10,000, its inventors claim.

To prolong their life Flash memory chips use a ‘wear-levelling’ process in which all cells are used equally, and worn out cells are ‘retired’ without disabling the whole chip.

The ferroelectric cells use a rewriting voltage of fewer than six volts, compared to about 20 volts for conventional chips.

Here’s the citation from KurzweilAI.net:

Japanese boffins develop long-life Flash
vnu.net, July 14, 2008

Flash memory chips with a potential lifetime of hundreds of years and a lower rewriting voltage have been developed by University of Tokyo scientists.

Current Flash chips are estimated to have a useful lifetime of around a decade or less for most applications.

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